The present invention relates to reporting the toner level in a print device toner cartridge and, more particularly, to reporting a calculated toner level from a first portion of the toner cartridge and reporting a sensed toner level from the remaining portion of the toner cartridge.
Consumable items in printing devices mostly include xe2x80x9cmarking agentxe2x80x9d components that are consumed with each printed page as part of the printed product, and rotating components that deteriorate over time as a result of wear and tear. Marking agent consumables include ink, wax, powder toner, thermal agents, and the like. Marking agents are often housed in some type of cartridge, such as a toner cartridge, and dispensed onto rotating components that transfer the agents to a print medium during a printing process. As a marking agent is depleted, it is useful to have information about the amount of agent remaining in a cartridge in order to approximate the number of pages available for printing during the remaining life of the cartridge. Various methods exist that provide information regarding the remaining useful life of a cartridge.
A page counting method does not involve direct measurement information about the level of toner (i.e., marking agent) present in a cartridge. Instead, this method provides an expected life span for a toner cartridge measured by the number of pages that the cartridge is expected to print. The life span is reduced by one page for each page that is printed. A disadvantage of this simple method is that it can be inaccurate.
The inaccuracy of this method can result from at least two factors. First, the expected number of pages available from a toner cartridge is a rough estimate set by the cartridge designer based on numerous examples of like cartridges. The actual number of available pages can vary significantly from cartridge to cartridge. Second, the amount of toner put on each printed page may vary dramatically from page to page. These factors often mean that more or less toner is left in a cartridge than expected, which can result in significant differences in the number of pages expected to be printed and the number of pages that can actually be printed by a given cartridge.
A pixel counting method also does not involve direct measurement information about the level of toner present in a cartridge. Rather, this method starts with an assumed maximum number of pixels available to be expended over the life of the cartridge. In a color laser printer, the number of pixels expended can be estimated by tracking the number of laser pulses used to discharge a photoconductor drum (OPC). A finite number of laser pulses is used to discharge the OPC in preparation to attract a pixel (or dot) of toner. The number of laser pulses can be measured for each printed page, and the appropriate number of pixels can be subtracted from the maximum pixels available, thereby providing a measure of the percentage of pixels (i.e., toner) remaining in the cartridge.
Unfortunately, this method suffers disadvantages similar to the previous method. The maximum number of available pixels is assumed by the cartridge designer based on numerous examples of like cartridges. The actual number of available pixels can vary significantly from cartridge to cartridge. In addition, counting laser pulses can be an inaccurate method of determining the number of expended pixels on a printed page. Although the error per page may be slight, it can add up over the life of the cartridge (e.g., 10,000 printed pages) and create a significant difference in the expected percentage of toner available and the actual percentage of toner available. Moreover, the largest errors are seen toward the end of the cartridge life cycle, which is the time when it is most important to have accurate toner level information.
Another method of determining the toner level within a cartridge utilizes antenna sensor technology. This method provides direct information about the level of toner in a cartridge and is therefore more accurate than the previously discussed methods. The level of toner in a cartridge is determined by passing current from one end of the cartridge to the other through an antenna. The current induces voltage signals in coils within the cartridge that are proportional to the amount of toner present in the cartridge. Although this direct measurement of the toner level is beneficial, it too has disadvantages.
One disadvantage of using antenna sensor technology is its cost. Where page counting and pixel counting methods can be implemented by simple software executing on pre-existing computer hardware, the antenna technology requires the installation of hardware into each toner cartridge. In addition to the cost of the antenna hardware itself, there are design costs associated with fitting the hardware inside different cartridges of varying shapes and sizes. Moreover, the physical size constraints of some cartridges prohibit antenna sensor coverage throughout the entire cartridge, thus limiting toner level sensing to only part of the cartridge.
Accordingly, the need exists for a cost effective way to determine the level of toner present throughout the life of a toner cartridge in a manner that permits a high level of predictability as to the remaining useful life of the toner cartridge.
A printer system calculates toner (or other marking agent) levels in a toner cartridge over an upper portion of the cartridge, while sensing toner levels in the remaining lower portion of the cartridge. The system provides the accuracy of a sensed toner environment when it is most needed (i.e., during the latter portion of a toner cartridge lifespan). A less accurate, but useful method of calculating the toner level is employed during the earlier stages of the toner cartridge lifespan. Thus, the system avoids the high cost associated with a fully sensed toner environment while providing the increased accuracy of a sensed toner environment when it is most beneficial to the system user.
Early in the lifespan of a toner cartridge, the system reports toner levels using a counting method. The method calculates toner levels based on the estimated availability and usage of page capacity or pixel capacity for the cartridge. Therefore, the calculations provide an estimated toner level for the system to report.
In addition, the system monitors readings from a partial sensor configured to sense toner levels in the lower portion of the toner cartridge. While the actual toner level remains above the upper threshold of the lower/sensed portion of the cartridge, the sensor readings generally indicate that the toner level is at 100% of the lower portion of the cartridge. Thus, the sensor readings become meaningful only when the actual toner level drops below the upper threshold of the sensed portion of the cartridge.
Because the estimated toner level is less accurate than the sensed toner level, the system switches from reporting the estimated toner level to reporting the sensed toner level at the first indication that the sensor is in play. That is, at the first indication that the sensor readings are meaningful, the system begins reporting toner levels based on the sensor readings.
There are three indications that prompt the system to switch from reporting the estimated toner level to reporting the sensed toner level. The first is when the estimated toner level drops below the threshold level of the lower portion of the cartridge, and the sensed toner level remains at the threshold. The second is when the estimated toner level remains above the threshold, and the sensed toner level drops below the threshold. The last indication, which is unlikely based on the inherent inaccuracy of the counting method, is when both the estimated and sensed toner levels drop below the threshold at the same time. Under each of these circumstances, the system begins reporting the sensed toner level.
The system continues reporting the sensed toner level throughout the remaining lifespan of the cartridge, providing a user with the more accurate toner level information when it is most useful.